The present invention relates to methods of beneficiating drilling fluids that comprise low-quality clay and high-quality clay.
Swellable clays, also referred to herein as clays, are a major component of aqueous-based drilling fluids. Swellable clays provide several functions including lubricating and cooling the drill bit, viscosifying the fluid, controlling fluid loss by forming a filter cake along the wellbore, and suspending drilled solids. There are several types of clays (e.g., bentonite, kaolin, and Fuller's earth) that have varying levels of performance in each of these functions. Further, within an individual type of clay the performance in each of these functions can vary based on the source of the clay, e.g., Wyoming bentonite versus Arkansas bentonite.
In some instances, the quality of the clay may be enhanced (i.e., beneficiated) through extrusion methods, aging methods, and the like. Extrusion involves mechanically shearing the clay through a grinder (similar to a meat grinder), which is expensive and sensitive to conditions like moisture levels, feed rate, and die size. Further, there are no easily identified qualities of the original clay that allow for predicting the extent of the quality enhancement or if quality enhancement will occur.
Aging involves exposing the clay to sun for several months, which sounds straightforward, but given the volumes, e.g., 80,000 ton piles, mixing the clay to provide evenly aged clay is energy intensive and may yield variable results. Further, the cost and space of inventorying clay can be high and requires predictive business modeling to have clay at the right level of aging when needed. Because of these drawbacks, the current methods for beneficiating low-quality clay are used sparingly. As such, drilling fluids use higher concentrations of low-quality clay, which increases costs and decreases the carrying capacity of the drilling fluid (e.g., the amount of cuttings that can be removed from the wellbore during drilling).